In recent years, organic electroluminescent (EL) displays which make use of organic electroluminescence have been the focus of attention as one of next-generation flat panel displays to replace liquid-crystal displays.
The organic EL displays include an organic EL panel in which a plurality of display pixels are disposed in a matrix. The display pixel includes an organic EL element and a drive transistor which supplies drive current according to a pixel signal to the organic EL element.
In active-matrix display devices such as organic EL displays, thin-film transistors (TFTs) are used as drive transistors. In a TFT, a threshold voltage of the TFT shifts over time due to stress caused by, for example, a gate-source voltage when the TFT is powered up. The shift of the threshold voltage with the passage of time may cause variation in the amount of current supplied to an organic EL element, and thus affects luminance control of the display device, leading to deterioration of the display quality.
In the organic EL display, in order to prevent deterioration of the display quality, a cumulative value of a pixel signal (hereinafter referred to as “cumulative value” as appropriate) is calculated, and a pixel signal is corrected using the cumulative value. The pixel signal is a signal included in a video signal indicating an image of one frame, and includes chromaticity, saturation, a gradation value, etc., of one pixel.